Maintenance activity is commonly organized into “line maintenance” and “hangar maintenance”. Hangar maintenance is undertaken during preprogrammed inspections. Such maintenance operations are often conducted at the main base of the company that utilizes the aircraft. Line maintenance is performed between two flights, wherever the aircraft is located. The main purpose of line maintenance is urgent corrective actions, whereas hangar maintenance makes it possible to perform scheduled tasks as well as deferred corrective actions. In general, therefore, non-urgent corrective actions are systematically deferred until the next inspection.
However, the maintenance policies such as presented in the foregoing are not always optimal. By deferring corrective actions until the next inspection, line maintenance increases the risk that additional degradation will cause a flight delay or cancellation, or other disturbances.